Timmy sentiment phases theory: (1) Shoots you and runs away (2) Fires warning shots, But fires at enemies 1st if there's any around (3) Trusts you enough to not shoot you (4) Full sentiment
For the sake of story continuity they'd have to make him essentially immortal, unlike virginia or kelvin. Given he's a superhuman, this would be fine. Plus maybe as a result of you "besting" him in combat by "killing" him, he's forced to use his powers on you and just bodies you